So his death Saturday on his 75th birthday, at Rush University Medical Center’s Horizon Hospice on South Paulina Avenue, left many Chicagoans wondering how the void he has left could possibly be filled. He died of “a rare heart disease,” cardiac amyloidosis, said Marilyn Damon, his wife.

“I truly cannot imagine Chicago entertainment without Jimmy Damon, because he personified Chicago entertainment,” said Denise McGowan Tracy, an impresario who was mentored by the singer since the early 1980s.

“When we started ‘Monday Night Live’ at Petterino’s,” added Tracy, referring to the weekly cabaret sessions at the Loop restaurant, “he came down (wearing) a T-shirt that said: ‘Monday Night Live at the Playboy Club.’

“And I said, ‘Oh my God, we stole your idea.’

“But he said: ‘I’m thrilled.’”

As usual, Damon had been there first. Indeed, he championed jazz-swing standards in uncounted Chicago venues since the mid-1960s, when he moved here from his native Memphis. Along the way, he won the admiration of some formidable musical talents.

“I thought he was terrific,” said the revered Chicago singer-pianist Audrey Morris. “He was great at the personal part of it – expressing himself, and not sounding like someone else.”

Said vocalist-guitarist Frank D’Rone, “He knew how to get to people.”

Added cabaret performer Carla Gordon, who sang alongside Damon in recent years: “He had great chops, but his heart always led him.”

That about sums up the appeal of Damon, who owned a resplendent baritone and used it to considerable emotional effect. When Damon stepped into the spotlight, he did not hold back.

This tendency made him a tad overbearing early in his Chicago career, in the 1960s and ’70s, as Damon was quick to acknowledge.

“I was still learning how to be an entertainer, how to connect with an audience, how to put things together,” he told the Tribune in 1998. “In those days, I was the lounge lizard that was becoming Jimmy Damon.”

According to Damon and many others, comic actor Bill Murray caught Damon’s lounge-lizard act at the long-gone Cousins’ Club, on East Superior Street, when Murray still was honing his craft at Second City. Thus Murray found the inspiration for the unctuous lounge singer Murray later would famously spoof on “Saturday Night Live.”

Not that Damon minded.

“I wasn’t upset,” he said in the Tribune interview, winding up for the punch line. “I just wish he’d sent me a check. He owes me a lot of money.”

That a child-prodigy country singer from Memphis would eventually become the quintessential big-city crooner defies the imagination, but show business careers sometimes unfold in unexpected ways.

Damon had gotten off to a quick start back home in Tennessee, singing as young Jimmy Demopoulos at Kiwanis Clubs and church functions. Elvis Presley and Johnny Cash would frequent the family’s diner, the New York Café, and young Demopoulos was smitten.

“At night we’d often go to hear singers who worked for my father (at the diner) during the day,” Damon said in the 1998 Tribune interview. “We’d listen to country. We’d go to Beale Street and listen to black music – blues, jazz. That’s where the action was.”